A co - extractant for extracting boric acid from salt lake brine and a method for extracting boric acid

Abstract

The present invention discloses an ionic liquid co-extraction agent for extracting boric acid from salt lake brine and a method for extracting boric acid from salt lake brine by using the ionic liquid as a co-extraction agent. Using an ionic liquid to enhance the extractant has the characteristics of good selectivity, high efficiency and low cost in boron extraction from salt lake brine, and has broad application prospects. Applying this co-extraction agent can enhance the extraction effect of the boric acid extraction process from salt lake brine and improve the single-stage extraction efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of salt lake chemical industry, and particularly relates to a co - extractant for extracting boric acid from salt lake brine and a method for extracting boric acid. Background Art

[0002] In Qinghai Province, the boron resource reserves are abundant, ranking second in the country. The large - scale ore deposits mainly include salt lakes such as Dachaidan Lake, Xiaochaidan Lake, Yiliping, Xitieshan Lake and Qarhan. Boric acid is an industrial boride with extremely wide uses. Boric acid is mainly used in the glass manufacturing industry, and in the enamel and ceramic industries to enhance the luster and firmness of products. In the steel industry, boron - added boron steel has high hardness and good rolling properties and can replace nickel steel. It is used as a bactericide in medicine. In addition, it can also be used as a wood preservative. It is used as a boron fertilizer in agriculture. It also has wide uses in metal welding, leather manufacturing, capacitors, electroplating, cosmetics and other manufacturing aspects. Boric acid is the main raw material for manufacturing various boron compounds. After decades of exploitation of solid boron ore resources in Qinghai Province, they have now been basically exhausted, while a large amount of boron is by - produced during the process of extracting lithium from salt lake brine and has not been industrially utilized.

[0003] Xitieshan Lake is characterized by rich potassium, boron and lithium. The identified lithium resource amount (calculated as lithium chloride) is 2.63 million tons, the potassium resource amount (calculated as potassium chloride) is 20.73 million tons, and the boron resource amount (calculated as boron trioxide) is 1.55 million tons. The efficient development and utilization of lithium, potassium and boron resources can not only improve the comprehensive utilization benefits of salt lakes, but also be a powerful component in building a world - class salt lake industrial base in Qinghai. Qinghai Zhongxin Guotai Technology Development Co., Ltd. started the operation of acidifying old brine to produce boric acid in April 2016. In 2017, about 25,000 tons of crude boric acid were produced throughout the year, with an average B2O3 grade of 18.6% and high impurity content. Using the hot - dissolution and cold - crystallization process, about 4,000 tons of refined boric acid products can be produced. Although partial refinement of boric acid has been achieved, due to limitations in technology and equipment, the quality of refined boric acid products cannot be effectively improved.

[0004] The modern industry has an increasing demand for boron, and a mature and efficient boron development technology is very meaningful. Boron elements are mainly distributed in solid ores and liquid ores. With the large - scale exploitation of boron ores, the boron elements in solid ores have been almost exhausted. It is very important to develop a mature and efficient technology to extract boron elements from liquid ores. The research on the development and utilization of boron resources in salt lake brine in China is still in its initial stage. The continuous development and utilization of boron ore resources and the immaturity of technology have reduced China's high - quality boron resources, and at the same time caused waste of resources and pollution of the salt lake environment. Therefore, how to greenly and efficiently utilize boron resources, especially extracting boron resources from salt lake brine, has become increasingly urgent.

[0005] Currently, the main technologies for extracting boron from salt lake brine include acidification crystallization method, precipitation method, flotation method, ion exchange method, solvent extraction method, etc. However, the extraction rate of boron by the acidification crystallization method is only 50% - 60%, which is only applicable to raw brine with a relatively high boron content; the precipitation method consumes a large amount of acid; the ion exchange method is restricted by process and cost in industrial production. The solvent extraction method is less restricted by the boric acid content in the solution, and has a short process flow, simple production equipment, and easy operation. It is an ideal boron extraction method with broad application prospects. However, the monohydric alcohol extractant used has problems such as low single-stage extraction rate and the need for a large number of extraction stages; this causes a large loss of the solvent, and the lost extractant pollutes the aqueous phase after entering the aqueous phase. Improving the single-stage extraction rate is an important problem to be solved. The dihydric alcohol extractant has poor viscosity difference, high dissolution loss rate, and poor oil solubility, which restricts industrial application to a certain extent. Summary of the Invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and provide an ionic liquid co-extractant for extracting boric acid from salt lake brine and a method for extracting boric acid from salt lake brine using this ionic liquid as a co-extractant. Using ionic liquids to enhance the extractant has the characteristics of good selectivity, high efficiency, and low cost in extracting boron from salt lake brine, and has broad application prospects. Applying this co-extractant can enhance the extraction effect of the boric acid extraction process from salt lake brine and improve the single-stage extraction efficiency.

[0007] The present invention is achieved through the following technical solutions:

[0008] A co-extractant for extracting boric acid from salt lake brine, the co-extractant is an ionic liquid, and the anions in the ionic liquid include but are not limited to chloride ions, acetate ions, hydrogen phosphate ions, dihydrogen phosphate ions, sulfate ions, bisulfate ions, carbonate ions, bicarbonate ions, methylsulfonate ions, trifluoromethylsulfonate ions, etc.;

[0009] The cations of the ionic liquid co-extractant are 3-methylimidazole cations with different side chain lengths and pyridine cations with different side chain lengths, etc.; its structural formula is,

[0010]

[0011] Among them: both R1 and R2 are straight-chain alkyl groups of C 11 ~C 20

[0012] In the above technical solution, the anions of the ionic liquid are bisulfate ions and methylsulfonate ions;

[0013] For the cations of the ionic liquid, R1 and R2 are straight-chain alkyl groups of C 12 ~C 16 ​​

[0014] A method for extracting boric acid from salt lake brine, using the co - extractant for extracting boric acid from salt lake brine described in the above - mentioned technical solution.

[0015] Research has found that when the anion of the ionic liquid is methylsulfonate ion and the cation is within the preferred range, the single - stage extraction rate of boric acid can be significantly increased from 54% without a co - extractant to 90% - 95%; when the anion of the ionic liquid is hydrogen sulfate ion and the cation is within the preferred range, the single - stage extraction rate of boric acid can be significantly increased to 92% - 95%.

[0016] A method for extracting boric acid from salt lake brine, using the ionic liquid in the above - mentioned technical solution as a co - extractant, comprising the following steps:

[0017] Step 1: Mix the co - extractant, extractant, and diluent to obtain an extraction organic phase; the volume ratio of the extractant to the diluent is 1:(0.25 - 1.5); preferably 1:(0.6 - 1);

[0018] The addition amount of the co - extractant relative to the extractant is 1 g / (30 - 60) mL, preferably 1 g / (40 - 50) mL;

[0019] Mix the extraction organic phase with acidified salt lake brine for mixed extraction, and after phase separation, obtain a boric - acid - loaded organic phase and raffinate water;

[0020] Step 2: Mix the boric - acid - loaded organic phase with a stripping agent for stripping extraction, and after phase separation, obtain an aqueous phase containing boric acid and a lean organic phase;

[0021] The stripping agent is a neutral or weakly acidic aqueous solution.

[0022] In the above - mentioned technical solution, the extractant is a monohydric fatty alcohol and / or a dihydric fatty alcohol;

[0023] The monohydric fatty alcohol is preferably at least one of isoamyl alcohol and isooctyl alcohol;

[0024] The dihydric fatty alcohol is preferably at least one of 1,2 - diol and 1,3 - diol.

[0025] In the above - mentioned technical solution, the diluent is a hydrophobic organic solvent with a kinematic viscosity not higher than 8 mm 2 / s at 20 °C, preferably aviation kerosene.

[0026] In the above - mentioned technical solution, the pH value of the acidified salt lake brine is 2 - 3, preferably 2 - 2.6;

[0027] The process of acidifying the salt lake brine uses hydrochloric acid for acidification.

[0028] In the above technical solution, during the process of mixing and extracting the extraction organic phase with the acidified salt lake brine, the volume ratio of the extraction organic phase to the acidified salt lake brine is preferably 1∶(1 - 1.2).

[0029] In the above technical solution, during the process of mixing and extracting the extraction organic phase with the acidified salt lake brine, the extraction temperature is 20 - 40°C, and the preferred temperature is 20 - 25°C; the extraction time is preferably 20 - 30 min.

[0030] In the above technical solution, the pH value of the stripping agent is 6 - 7; the preferred stripping agent is deionized water.

[0031] In the above technical solution, during the process of mixing and stripping the boric acid-loaded organic phase with the stripping agent, the volume ratio of the stripping agent to the boric acid-loaded organic phase is preferably 1∶(1 - 1.2).

[0032] In the above technical solution, during the process of mixing and stripping the boric acid-loaded organic phase with the stripping agent, the stripping temperature is 20 - 40°C, the preferred temperature is 20 - 25°C, and the stripping time is preferably 20 - 30 min.

[0033] The advantages and beneficial effects of the present invention are as follows:

[0034] The key to solvent extraction is the selection of the extraction system. Therefore, for different types of salt lakes, it is a current research hotspot to select an extraction system with good extraction performance and low water solubility. The basic mechanism of the method for extracting boric acid from salt lake brine in the present invention is (illustrated by taking isooctanol as the extractant):

[0035] (1) The acidified salt lake brine will react with isooctanol to form mono-isooctyl borate, di-isooctyl borate, and tri-isooctyl borate (collectively referred to as borate esters); these esters have extremely low solubility in water but good solubility in the organic phase, so that boric acid can be extracted into the organic phase in the form of borate esters.

[0036] (2) However, under acidic conditions, borate esters are prone to hydrolysis reactions, and this hydrolysis process is usually carried out in two steps: the first step of hydrolysis generates hydrogen ions and borate ester anions, and then further hydrolysis generates boric acid and isooctanol.

[0037] (3) The micelles formed by the ionic liquid (co-extractant) dissolved in the organic phase selectively extract the borate esters formed at the phase interface, accelerating the diffusion of borate esters, thereby achieving the purpose of strengthening the extraction of boric acid.

[0038] The ionic contents in different types of salt lake brines may vary significantly or be similar, but other ions have no obvious impact on this system. Therefore, the extraction system disclosed in this application is not only applicable to a specific type of salt lake brine during application, but can be applied to all salt lake brines containing boron.

[0039] In the technical solution of the present invention, in the cationic structural formulas (I) and (II) of the ionic liquid co - extractant, both are hydrophobic cations and contain N atoms. The N atoms can form hydrogen bonds with the complex borate ester, thereby achieving the technical effect of selective extraction.

[0040] The method for extracting boric acid from salt lake brine in the present invention has the following beneficial effects compared with the prior art:

[0041] 1. The present invention innovatively provides an ionic liquid as a co - extractant and uses it to extract boric acid from salt lake brine, providing a new method for extracting boric acid, which can greatly improve the single - stage extraction rate of boric acid;

[0042] 2. The ionic liquid co - extractant provided by the present invention can significantly increase the single - stage extraction rate of boric acid from 54% without a co - extractant to 90% - 95%;

[0043] 3. The carbon number of the alkyl chain of the cation of the ionic liquid co - extractant provided by the present invention is greater than 10, and it is insoluble in water. The co - extractant will not be lost during the extraction process and will not affect the quality of the boric acid product during the stripping process;

[0044] 4. The method for extracting boric acid provided by the present invention has simple production equipment and convenient operation in the actual production process, and can achieve high - value recovery of boron from salt lake brine. Detailed Embodiments

[0045] To enable those skilled in the art to better understand the solution of the present invention, the technical solution of the method for extracting boric acid from salt lake brine will be further described below in conjunction with specific embodiments.

[0046] The pH value of the Qinghai salt lake brine used in each experiment of the present invention is 4.2, which contains 28.5 g / L of boric acid, and the main components are shown in Table 1.

[0047] Table 1 Main components of Qinghai salt lake brine

[0048] Ingredient <![CDATA[H3BO3]]> <![CDATA[Mg 2+ > <![CDATA[Li + > <![CDATA[SO4 2- > <![CDATA[Cl - > <![CDATA[Content / g·L -1 > 28.5 109.9 1.9 27 287.4

[0049] Example 1

[0050] Adjust the pH value of 20 mL of Qinghai salt lake brine to 2.6 with 2 mol / L hydrochloric acid to obtain acidified salt lake brine;

[0051] 10 mL of isooctyl alcohol was used as an extractant and 10 mL of aviation kerosene was used as a diluent. The two were fully mixed, and then 0.25 g of 1-dodecyl-3-methylimidazole hydrogen sulfate was dissolved in the mixed solution as an auxiliary extractant by ultrasonic vibration to form an extraction organic phase;

[0052] The acidified salt lake brine was mixed with the extracted organic phase, and subjected to constant temperature shaking extraction in a water bath at 20°C for 20 minutes. After standing and stratification, an extracted organic phase containing borate anions was obtained. After measurement and calculation, the extraction rate was 92.6%.

[0053] 20 mL of deionized water was used as the stripping agent, and the stripping was carried out in a water bath at 20°C with constant temperature shaking. The stripping time was 20 minutes, and after standing and stratification, an aqueous solution containing boric acid was obtained. After measurement and calculation, the stripping rate was 74.0%.

[0054] Embodiment 2

[0055] 20 mL of Qinghai salt lake brine was acidified with 2 mol / L hydrochloric acid to adjust the pH value to 2.6 to obtain acidified salt lake brine;

[0056] 10 mL of isooctyl alcohol was used as an extractant and 10 mL of aviation kerosene was used as a diluent. The two were fully mixed, and then 0.25 g of 1-dodecyl-3-methylimidazolium methylsulfonate was dissolved in the mixed solution as an auxiliary extractant by ultrasonic oscillation to form an extraction organic phase;

[0057] The acidified salt lake brine was mixed with the extracted organic phase, and subjected to constant temperature shaking extraction in a water bath at 20°C for 20 minutes. After standing and stratification, an extracted organic phase containing borate anions was obtained. The extraction rate was determined to be 90.0%.

[0058] 20 mL of deionized water was used as the stripping agent, and the stripping was carried out in a water bath at 20°C with constant temperature shaking. The stripping time was 20 minutes, and after standing and stratification, an aqueous solution containing boric acid was obtained. After measurement and calculation, the stripping rate was 72.4%.

[0059] Embodiment 3

[0060] 20 mL of Qinghai salt lake brine was acidified with 2 mol / L hydrochloric acid to adjust the pH value to 2.6 to obtain acidified salt lake brine;

[0061] 12 mL of isooctyl alcohol was used as an extractant and 8 mL of aviation kerosene was used as a diluent. The two were fully mixed, and then 0.25 g of 1-tetradecyl-3-methylimidazole hydrogen sulfate was dissolved in the mixed solution as an auxiliary extractant by ultrasonic vibration to form an extraction organic phase;

[0062] The acidified salt lake brine was mixed with the extracted organic phase, and subjected to constant temperature shaking extraction in a water bath at 20°C for 20 minutes. After standing and stratification, an extracted organic phase containing borate anions was obtained. After measurement and calculation, the extraction rate was 93.5%.

[0063] 20 mL of deionized water was used as the stripping agent, and the stripping was carried out in a water bath at 20°C with constant temperature shaking. The stripping time was 20 minutes, and after standing and stratification, an aqueous solution containing boric acid was obtained. After measurement and calculation, the stripping rate was 76.2%.

[0064] Embodiment 4

[0065] 20 mL of Qinghai salt lake brine was acidified with 2 mol / L hydrochloric acid to adjust the pH value to 2.6 to obtain acidified salt lake brine;

[0066] 12 mL of isooctyl alcohol was used as an extractant and 8 mL of aviation kerosene was used as a diluent. The two were fully mixed, and then 0.25 g of 1-tetradecylpyridinium hydrogen sulfate was dissolved in the mixed solution as an auxiliary extractant by ultrasonic vibration to form an extraction organic phase;

[0067] The acidified salt lake brine was mixed with the extracted organic phase, and subjected to constant temperature shaking extraction in a water bath at 20°C for 20 minutes. After standing and stratification, an extracted organic phase containing borate anions was obtained. After measurement and calculation, the extraction rate was 94.7%.

[0068] 20 mL of deionized water was used as the stripping agent, and the stripping was carried out in a water bath at 20°C with constant temperature shaking. The stripping time was 20 minutes, and after standing and stratification, an aqueous solution containing boric acid was obtained. After measurement and calculation, the stripping rate was 78.0%.

[0069] Embodiment 5

[0070] 20 mL of Qinghai salt lake brine was acidified with 2 mol / L hydrochloric acid to adjust the pH value to 2.6 to obtain acidified salt lake brine;

[0071] 11 mL of isooctyl alcohol was used as an extractant and 9 mL of aviation kerosene was used as a diluent. The two were fully mixed, and then 0.25 g of 1-hexadecylpyridinium hydrogen sulfate was dissolved in the mixed solution as an auxiliary extractant by ultrasonic vibration to form an extraction organic phase;

[0072] The acidified salt lake brine was mixed with the extracted organic phase, and subjected to constant temperature shaking extraction in a water bath at 20°C for 20 minutes. After standing and stratification, an extracted organic phase containing borate anions was obtained. After measurement and calculation, the extraction rate was 93.9%.

[0073] 20 mL of deionized water was used as the stripping agent, and stripping was carried out by constant temperature shaking in a water bath at 20 °C for 20 min. After standing for phase separation, an aqueous solution containing boric acid was obtained. Through measurement and calculation, the stripping rate was 76.9%.

[0074] Example 6

[0075] 20 mL of Qinghai Salt Lake brine was acidified with 2 mol / L hydrochloric acid to adjust the pH value to 2.6, obtaining acidified salt lake brine.

[0076] 11 mL of isooctanol was used as the extractant and 9 mL of aviation kerosene was used as the diluent. The two were fully mixed, and then 0.25 g of 1-hexadecylpyridinium methyl sulfonate was dissolved in the above-mentioned mixed solution by ultrasonic oscillation to form the extraction organic phase.

[0077] The acidified salt lake brine was mixed with the extraction organic phase, and extraction was carried out by constant temperature shaking in a water bath at 20 °C for 20 min. After standing for phase separation, an extraction organic phase containing borate anions was obtained. Through measurement and calculation, the extraction rate was 92.2%.

[0078] 20 mL of deionized water was used as the stripping agent, and stripping was carried out by constant temperature shaking in a water bath at 20 °C for 20 min. After standing for phase separation, an aqueous solution containing boric acid was obtained. Through measurement and calculation, the stripping rate was 73.6%.

[0079] Comparative Example

[0080] Compared with Example 1, the difference was only that an ionic liquid co-extractant was not added during the extraction process.

[0081] 20 mL of Qinghai Salt Lake brine was acidified with 2 mol / L hydrochloric acid to adjust the pH value to 2.6, obtaining acidified salt lake brine.

[0082] 10 mL of isooctanol was used as the extractant and 10 mL of aviation kerosene was used as the diluent. The two were fully mixed by ultrasonic oscillation to form the extraction organic phase.

[0083] The acidified salt lake brine was mixed with the extraction organic phase, and extraction was carried out by constant temperature shaking in a water bath at 20 °C for 20 min. After standing for phase separation, an extraction organic phase containing borate anions was obtained. Through measurement and calculation, the extraction rate was 54.0%.

[0084] 20 mL of deionized water was used as the stripping agent, and stripping was carried out by constant temperature shaking in a water bath at 20 °C for 20 min. After standing for phase separation, an aqueous solution containing boric acid was obtained. Through measurement and calculation, the stripping rate was 78.0%.

[0085] Both dihydric alcohols and monohydric alcohols contain hydroxyl groups and can react with boric acid to form esters, which are then extracted. Therefore, both monohydric fatty alcohols and dihydric fatty alcohols can be used. However, due to the higher cost of dihydric alcohols, dihydric alcohols are not used as examples in the specific embodiments.

[0086] The above provides an exemplary description of the present invention. It should be noted that without departing from the core of the present invention, any simple deformation, modification, or equivalent substitution that can be made by those skilled in the art without creative efforts falls within the protection scope of the present invention.

Claims

1. An auxiliary extractant for extracting boric acid from salt lake brine, characterized in that, The co - extractant is an ionic liquid, and the anion in the ionic liquid is hydrogen sulfate ion or methyl sulfonate ion; The cation of the ionic liquid is 3 - methylimidazolium cation or pyridinium cation; its structural formula is, Wherein: both R1 and R2 are straight-chain alkyl groups of C 11 ~C 20 .

2. The auxiliary extractant according to claim 1, characterized in that, The anion of the ionic liquid is hydrogen sulfate ion and methyl sulfonate ion; R1 and R2 of the cation of the ionic liquid are linear alkyl groups with C 12 ~C 16 .

3. A method for extracting boric acid from salt lake brine, characterized in that, Use the co - extractant for extracting boric acid from salt lake brine according to claim 1 or 2.

4. A method for extracting boric acid from salt lake brine, characterized in that, Use the co - extractant for extracting boric acid from salt lake brine according to claim 1 or 2, including the following steps: Step 1, mix the co - extractant, extractant and diluent to obtain an extraction organic phase; the volume ratio of the extractant to the diluent is 1∶(0.25 - 1.5); The addition amount of the co - extractant relative to the extractant is 1 g / (30 - 60) mL; Mix the extraction organic phase with the acidified salt lake brine for mixed extraction, and after phase separation, obtain a boric acid - loaded organic phase and raffinate water; Step 2, mix the boric acid - loaded organic phase with a stripping agent for stripping extraction, and after phase separation, obtain an aqueous phase containing boric acid and a lean organic phase; The stripping agent is a neutral or weakly acidic aqueous solution.

5. The method for extracting boric acid from salt lake brine according to claim 4, characterized in that, The extractant is a monohydric aliphatic alcohol and / or a dihydric aliphatic alcohol; The monohydric aliphatic alcohol is at least one of isoamyl alcohol and isooctyl alcohol; The dihydric aliphatic alcohol is at least one of 1,2 - diol and 1,3 - diol.

6. The method for extracting boric acid from salt lake brine according to claim 4, characterized in that, The diluent is a hydrophobic organic solvent with a kinematic viscosity not higher than 8 mm 2 / s at 20°C.

7. The method for extracting boric acid from salt lake brine according to claim 4, characterized in that, The pH value of the acidified salt lake brine is 2 - 3; Hydrochloric acid is used for acidifying the salt lake brine during the acidification process.

8. The method for extracting boric acid from salt lake brine according to claim 4, characterized in that, During the process of mixing the extraction organic phase with the acidified salt lake brine for mixed extraction, the volume ratio of the extraction organic phase to the acidified salt lake brine is 1∶(1 - 1.2).

9. The method for extracting boric acid from salt lake brine according to claim 4, characterized in that, During the process of mixing the extraction organic phase with the acidified salt lake brine for mixed extraction, the extraction temperature is 20 - 40 °C; the extraction time is 20 - 30 min.

10. The method for extracting boric acid from salt lake brine according to claim 4, characterized in that, The pH value of the stripping agent is 6 - 7; the stripping agent is deionized water; During the process of mixing the boric acid - loaded organic phase with the stripping agent for stripping extraction, the volume ratio of the stripping agent to the boric acid - loaded organic phase is 1∶(1 - 1.2); During the process of mixing the boric acid - loaded organic phase with the stripping agent for stripping extraction, the stripping temperature is 20 - 40 °C, and the stripping time is 20 - 30 min.

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